Allylic trichloroacetamide

Stereoselective transformation of allylic alcohol to allylic trichloroacetamide via trichloroacetimidate intermediate. 

The Overman Rearrangement allows the conversion of readily available allylic alcohols into allylic amines by a two-step synthesis involving the rearrangement of an allylic trichloroacetimidate to an allylic trichloroacetamide with clean 1,3-transposition of the alkenyl moiety. 

Hetero-Claisen rearrangement. The rearrangement of allylic trichloroacetimidates (8.35) to allylic trichloroacetamides (8.36) is an example of the hetero-Claisen rearrangement ... 

The rearrangement of allyl trichloroacetimidate into allyl trichloroacetamide (Overman rearrangement) has been used for the synthesis of amino sugars. For example, the trichloroace-... 

Asbase. KF on alumina effects the formation of trichloroacetimino ethers, and those derived from allylic alcohols readily undergo rearrangement to afford N-allyl trichloroacetamides. Xanthates are similarly prepared." ... 

Synthesh of amines by l3,3]sigmatropie rearrangement Trichloroacetimidic esters (2) of allylic alcohols (1) can be prepared in 80-100% yield (crude) by reaction with trichloroacetonitrile catal3rzed by the corresponding sodium or potassium alkoxide (O, ether). Inverse addition is preferred for secondary or tertiary alcohols. These esters undergo Claisen-type rearrangement at 25-140° to give allylic trichloroacetamides (3), in which the rrans-isomcr usually predominates. 

This reaction has been modified by using a chiral Pd(II) catalyst to yield allylic trichloroacetamides with good enantioselectivity. In addition, a [3,3]-sigmatropic rearrangement of alloxy iminodiaza-phospholidines has been implemented recently for the preparation of different nitrogen-containing molecules. ... 

Cobalt Oxazoline Palladacycles (COPs) are organocobalt-palladium complexes which catalyse the asymmetric rearrangements of non-chiral allylic trichloroacetamidates with very high enantiomeric selectivity (>90%) to provide chiral allylic amines [it is an aza-Claisen rearrangement, The Overman Rearrangement Overman Carpenter Org React 66 2005, Kirsch, Overman and Watson J Org Chem 69 8101 2004] and in the presence of phenols stereospecific cross-couphng also occurs to provide chiral phenoxyallyl ethers with veiy high (>90%) enantiomeric selectivity [Kirsch, Overman and White Org Lett 9 911 2007, Overman Carpenter Org React 66 2005]. 

Amino-2-deoxytetritol derivatives were also synthesised from allylic alcohols via formation of the trichloroacetamidate (20). lodocyclisation of (20) to (21) led ultimately to the ( )-erythro compound (22) whilst thermal [3,3]-sigmatropic rearrangement of (20) to the allylic trichloroacetamide (23) prior to cycli-... 

Reports on three useful transition metal catalysed cyclization routes to nitrogen heterocycles have appeared this year. In an extension of their earlier work on the synthesis of trichlorlnated T-butyrolactams by copper- or ruthenium-catalysed cyclization of -allyl-trichloroacetamides, Itoh and co-workers have now shown that... 

Formal [3,3]-sigmatropic rearrangement of the trichloroacetimidate of allylic alcohols to allylic trichloroacetamides, thereby transposing the hydroxyl and amino functions with good chirality transfer ... 

The Overman rearrangement of the disubstituted allylic trichloroace-timidates has also been used in the construction of trisubstituted carbons bearing a nitrogen substituent. For instance, heating a solution of the imidate 71 in refluxing xylene fiimishes the allylic trichloroacetamide 72 in good yield. Compound 72 is a precursor to aminocyclopentanol Ti ... 

COP-hfacac 50 (5.8 mg, 0.0065 mmol, 5 mol%) was added to a solution of ( )-hex-2-enyl 2,2,2-trichloroacetimidate (48, R = n-Pr) (40 mg, 0.13 mmol) in THF (0.05 mL), and the reaction vial was sealed, protected from light, and maintained at 50 °C. After 6 h, the orange solution was concentrated under reduced pressure. Purification of the residue by silica gel chromatography eluting with 10% ethyl acetate/90% hexanes to give the allylic trichloroacetamide 49 as a colorless solid (37 mg, 0.12 mmol, 93%). Chiral GC (Chiraldex y cyclodextrin trifluoroacetyl, 20 m x 0.25 m initial temperature 50 °C (1 min), final temperature 150 °C, 5 °C/min) showed that compound 48 had been formed in 96% ee. 

Yang has shown that the Overman rearrangement of allylic tri-chloroacetimidates to allylic trichloroacetamides can be efficiently catalysed by gold(i) chloride in water (Scheme 16.31). The rearrangement worked well under mild conditions (55 °C), and in short reaction times (2-6 h). The reaction work up appeared to be very simple as the final product was cleanly obtained by simple extraction. The authors were able to conduct the reaction on a gram scale using 2 mol% of the gold catalyst. 

Much more common, however, is the initiation of cyclization of A-allyl trichloroacetamides to y-lactams at low temperature, which often takes place in excellent 3ueld. It has been found that the y-lactam forming process takes place with only 10 mol % of CuCl when acetonitile is used as solvent and TMEDA as ligand. Sequential reactions consisting of the cyclization of N-allyl trichloroacetamide followed by the inter- or intramolecular carbon-carbon bond forming reactions at the a-position of the lactams were also reported eqs 6 and 7). ... 

This researeh was extended to include non-symmetrical amidinate complexes of the same type with mixed Cp and Cp ligands, such as the cationic species [Cp Ru 2-PrN=C(Me)NPr )RuCp(L)] (138 L = none, NCMe, CNBu , PMc3 BF4 salts). For 138 (L = CNBu ), there is NMR evidence that the isonitrile ligand switches between the ruthenium centers. Coordinatively unsaturated intermediates play a key role in catalytic processes, and thus complexes 138 (L = none PFe salt) and 135 (PFe salt) were found to catalyze the atom-transfer radical cyclization of A7-allyl trichloroacetamides. It was discovered that the greater protection offered by the steric bulk of the Cp" ligand led to the superior performance of 135 (PF salt). ... 

Related to the Overman esterification is the Overman rearrangement. The latter allows the conversion of readily available allylic alcohols into allylic amines by a two-step synthesis involving the rearrangement of an allylic trichloroacetimidate to an allylic trichloroacetamide with clean 1,3-transposition of the alkenyl moiety. Although this rearrangement can be thermally driven, addition of palladium salts lower the needed temperature. Chiral ligands such as proline-based diamines would lead to enantioenriched material. ... 

---